Add HDD build step to CI pipeline

Extended the CI pipeline to include a new job for building the hard disk drive (HDD) image alongside the existing ISO build, leveraging parallel processing with available CPU cores to optimize build time. This ensures automated packaging of the HDD format for broader deployment compatibility.

.gitlab-ci.yml

@@ -24,3 +24,11 @@ build_iso:
     paths:
       - bin/kumios.iso
 
+build_hdd:
+  stage: package
+  script:
+    - make -j$(nproc) hdd
+  artifacts:
+    paths:
+      - bin/kumios.hdd
+